Conventionally, technologies to detect various objects (for example, human faces and cars) from image data captured by cameras, etc. have been proposed. For instance, in technologies to detect objects, learning data to which features of objects to be detected is stored beforehand is used. In the object detection technology, whether or not an object to be detected exists in an image is determined by comparing the learning data with the captured image data.
Moreover, technologies to expedite processing of the above described image detection have been proposed. For example, according to the Japanese Laid-open Patent Publication No. 2004-246618, learning data is produced from a plurality of units of image data, and object detection is roughly performed for a search area in image data using the produced learning data. The Japanese Laid-open Patent Publication No. 2004-246618 discusses that a detailed object detection is performed only when it is determined that the image data may include an object to be detected.